1. Field of the Invention
The present invention relates to an operating valve assembly for a power steering unit, and more particularly to a rotary operating valve assembly.
2. Description of the Prior Art
As an operating system of the operating valve assembly of this kind can be simplified in construction, it is useful for an operating valve assembly for a power steering unit of a vehicle which is generally required to be compact. On the other hand, however, such an operating valve assembly has various problems in working in that its machining, particularly regarding its finishing with high accuracy of the inner and outer sleeves as main components of the assembly, is difficult and control of tools to be used for cutting the sleeves is troublesome.
A rotary valve for a power steering has been suggested to solve these problems.
Such a rotary valve, however, does not completely solve these problems, but encounters further difficulties in manufacture. With this rotary valve, separate parts such as a plug or the like must be used to form an oil chamber between inner and outer sleeves, resulting in increased number of parts and hence increased manufacturing cost for the parts to be machined with high accuracy. Accordingly, this rotary valve is in fact difficult and highly expensive to manufacture.